Hello, my name is***** and I have over 20 years of experience as a veterinarian. I am sorry to hear that Besta has stool stuck to her perianal area, which is getting worse every time she passes more stool, and is scooting on her bottom trying to remove the stool.
If she is very nervous and won't even let you look I do NOT recommend trying to cut anything off her. If she moves the wrong way you could end up cutting her instead.
I do recommend preparing a warm water and dilute antibacterial liquid soap bath and letting her sit in it for 10-15 minutes. Then run a gentle stream of warm water over her perianal to rinse and remove as much matter as possible. This might soften the matted stool enough for you to use a wide toothed comb to comb the rest of it off. This would be the safest way to go.
If she won't let you do this she might need an emergency visit to be sedated and clip/clean the area. This might not be just stuck stool, it may be an abscessed anal gland (scent glands located just inside the rectum) or a skin infection, and that may be why she doesn't want you to touch the area. Both of those would be very painful.
Please let me know if you have any further questions.
Thank you for the update on your girl, I am so pleased that a nice soak worked out well for her and there was nothing serious underneath it all. Please let me know if you have any further questions, Dr. Kara.